When machining a 10 mm diameter shaft, lets says a 100 mm length is machined in 1 minute, at 1,000 RPM. This means that the cutting length per minute is 100 mm/min.

- Click on the links below to learn more about the most common formulas used when turning!

Feed per revolution

Feed rate (when turning) is the amount of movement of the insert per revolution of the work.

As shown in the formula below, feed is ℓ (cutting length per minute) ÷n (main axis spindle speed). (Cutting length per minute) ÷ (RPM) is the movement of the cutting edge during one work rotation.

Cutting time (tc)

Cutting time is the time required to machine the workpiece.

As shown in the formula below, cutting time can be found by ℓm (workpiece length) ÷ ℓ(cutting length per minute).

Example: When cutting length per min is 20mm and workpiece length is 100mm; 100÷20=5. Cutting time is 5 minutes.

Cutting speed (vc)

Cutting speed (when turning) is the peripheral speed of the work and the amount of insert movement in metres per minute. (π x Dm) of the formula below is the periphery of the work. The periphery x n (RPM) is millimeters the cutting edge moves on the periphery of the work in a minute. It is usually expressed in m/min. Divide by 1,000 to change to m from mm.

Finished surface roughness (h)

Geometrical shape on the workpiece surface produced by the cutting edge is called theoretical roughness.

x